Pipes freeze first where cold reaches them: unheated cellars, crawl spaces under additions, exterior stone or brick walls and vacant houses. Ice plugs the crack, so the leak usually appears on the thaw. Before a freeze, keep heat on and know your main shut-off. If a pipe bursts, close the main valve, stay clear of wet outlets and call.
Key takeaways
- A frozen pipe often does not leak until it thaws, because ice plugs the split and the water comes through when the temperature rises, sometimes hours or days later.
- The coldest spots in an older house are exterior stone or brick walls, unheated vestibules and garages, cellars with bare supply lines, spaces under additions and any vacant or closed-up house.
- Philadelphia stayed below freezing for nearly a week in late January 2026, and the Philadelphia Water Department answered 147 water main breaks that month; in January 2018, after a stretch below freezing of more than seven days, it answered 366.
- Many utilities suggest keeping the heat on when you are away, with 55 degrees Fahrenheit or higher a commonly given figure, opening cabinet doors on exterior walls and knowing where your main shut-off is.
- If a pipe has burst, close the main valve first, keep out of water near outlets, take photos and call; a licensed plumber fixes the pipe and a restoration crew removes the water and dries the structure.
- A water main break in the street is the water utility's job, and it is a different problem from a frozen pipe inside the house.
Why do pipes freeze in older houses around Philadelphia?
Water inside a pipe freezes when the pipe's surroundings stay below 32 degrees Fahrenheit long enough. Older houses give cold more ways in: stone and brick exterior walls with little insulation, drafty vestibules, bare cellar supply lines and gaps around old pipe penetrations. Philadelphia's January average low is about 25.6 degrees Fahrenheit, so the cold is regular and not rare.
The 1991 to 2020 climate normals put the January average low in Philadelphia near 25.6 degrees Fahrenheit, with about 23.1 inches of snow in a season. An ordinary winter night is well below freezing, and a cold snap pushes the daytime high below it too.
Houses built before modern insulation standards lose heat through the walls. A supply line running through a stone or brick exterior wall sits inches from the outdoors, with little to protect it. A line in a cellar corner with a drafty window nearby has the same trouble.
Ice also forms a plug that traps water between the ice and a closed faucet, and the pressure builds. The pipe usually splits in the weakest spot, which is not always where the ice is. That is why a split can be a foot or two away from the cold spot that caused it.
Where do pipes freeze first in an older house?
The usual first points are supply lines in exterior stone or brick walls, pipes in unheated cellars and crawl spaces, lines under additions, garages and vestibules, outdoor spigots and any house left empty. Vacant homes are the worst case, since no one notices the leak. The table lists each location, why it freezes and what helps.
Walk the house on a cold day and note where it feels coldest. A kitchen sink on an exterior wall, a bathroom over a porch or a laundry in a back addition are classic problem spots. So is any pipe that runs through a space the furnace does not reach.
Cellars in older homes can look warm, since they sit below ground, but a bare line along a rim joist or near a window well can still freeze. Crawl spaces under additions often have no insulation and no heat, and the pipes there are exposed on all sides.
Outdoor spigots and hose connections are easy to forget. A hose left attached can trap water in the spigot and the pipe behind it. Disconnect hoses in October, before the first hard freeze.
| Location | Why it freezes | What helps |
|---|---|---|
| Exterior stone or brick wall | Little insulation, pipe sits near the outside surface | Open the cabinet doors on cold nights, add insulation where a plumber advises |
| Unheated cellar or crawl space | Cold air at the rim joist, bare lines, drafts at windows | Seal gaps, insulate exposed lines, keep the cellar above freezing |
| Under an addition or bay | Floor open to outside air, no heat | Insulate the floor and lines, and have the area checked before winter |
| Vestibule, garage or porch | No heat, doors opened often | Move or insulate lines, keep interior doors open to warm air |
| Outdoor spigot and hose line | Trapped water in the stem | Disconnect hoses in autumn and shut off and drain the line |
| Vacant or closed-up house | Heat turned down or off, no one to notice | Keep heat on, shut off and drain the system, or have someone check often |
What should you do before a hard freeze?
Find and test your main shut-off valve, keep the heat on, disconnect hoses and open cabinet doors on exterior walls during cold nights. If you will be away, many utilities suggest leaving the heat at 55 degrees Fahrenheit or higher and asking someone to check the house. Know where the main valve is before you need it.
Start with the main shut-off. In many older houses it is in the cellar, on the wall facing the street, and it may be stiff from years without use. Turn it off and on once in a mild month, so you know it works and everyone in the house knows where it is.
Let warm air reach the pipes. Open the cabinet doors under sinks on exterior walls, and keep interior doors open to rooms that have little heat. On the coldest nights, some people let a faucet drip slightly, but that is a measure for a plumber or your utility to advise on, not a guarantee.
If you plan to be away, the common advice is to keep the thermostat at 55 degrees Fahrenheit or higher. Another person checking the house is better still, since a leak found on day one is a small job and one found on day six is a big one.
- Test the main shut-off and tell everyone where it is
- Disconnect and drain outdoor hoses and spigots
- Open cabinet doors under sinks on exterior walls
- Keep the heat on, even in rooms you do not use
- Ask a neighbor or relative to check a house that will be empty
- Keep a plumber's number where you can find it
What should you do when a pipe is frozen but not yet burst?
Open the faucet the pipe feeds, so water has an exit as the ice melts, and warm the area with a hair dryer or a space heater placed safely away from anything flammable. Never use an open flame. If you cannot find the frozen section, or if you see any water, close the main valve and call a licensed plumber.
Frozen does not mean split. A pipe that has no water coming out at a faucet may be solid ice with no crack, and gentle warming can clear it. Open the tap before you start so melting water and pressure can escape.
Work from the faucet back toward the frozen section, which lets water drain as the ice melts. Keep any heat source away from insulation, paper and fabric, and do not leave a space heater unattended. A blowtorch or open flame is a fire risk, and it can damage the pipe or its joints.
If the pipe is inside a wall or ceiling and you cannot reach it, stop there. Thawing a hidden line can start a leak that you cannot see, so a licensed plumber is the right call. If a crew is already on its way for other damage, it can work around the plumber's visit.
Why does the leak usually show on the thaw?
Ice plugs the split in a frozen pipe and holds the water back. When the temperature rises or the heat comes back on, the ice melts and water pours through the crack. The leak often appears hours or days after the freeze, which is why people return from a trip to a flooded room.
A split pipe under pressure with ice in it behaves like a sealed container. The ice acts as a stopper, so nothing leaks while it holds. Once it melts, the pipe is open, and the water behind it is under full pressure.
The thaw can be a warm afternoon, a furnace cycling on or a weekend family returning to a house that was cold for days. The water can run for a long time before anyone sees it, especially in a wall or a ceiling.
That delay is why shutting off the water is the first move when anything looks wrong after a freeze. If water is running from a pipe, closing the main valve limits the damage faster than anything else you can do. The burst pipe and frozen pipe pages describe what the cleanup looks like.
What happened in January 2026, and what does it show?
An Arctic blast kept Philadelphia below freezing for nearly a week in late January 2026, and early 2026 brought snow at levels not seen in about ten years. The Philadelphia Water Department answered 147 water main breaks in January 2026. When the city last stayed below freezing for more than seven days, in January 2018, it answered 366.
Breaks flooded streets in Germantown, Roxborough, Manayunk, Fairmount, Point Breeze, Bustleton and North and Northeast Philadelphia, according to city reporting. A water main is the utility's pipe under the street, and repairing it is the utility's job, not a homeowner's or a restoration crew's.
The numbers are a reminder of scale, not a forecast. They show how many buried pipes fail across a city in a long cold spell, and that is separate from the lines inside a house. A frozen pipe inside your wall and a main break in the street can happen in the same week, and they call for different people.
If water is coming up in the street, call the water utility. If water is coming into your house, close the main valve and call a plumber and, for the cleanup and drying, a restoration crew.
What are the first steps when a pipe has burst?
Close the main shut-off valve, then open a faucet at the lowest point to drain the lines. Stay out of standing water near outlets, appliances or the panel, and turn off power to the area only if you can reach the panel dry. Take photos, call your insurer and then call a plumber and a restoration crew.
Time matters because every minute adds water. Closing the main valve is the single most useful action, and the sooner you do it, the smaller the cleanup.
Next, protect yourself and the house. Keep away from water that has reached a wall outlet, a light fixture or the electrical panel. If the ceiling below is sagging or bulging, move out from under it, since plaster that holds water can fall.
Photograph the damage before anything is moved, and call your insurer early. Coverage is decided by your insurer under your own policy, and the crew can give you moisture readings and photos for your claim. A licensed plumber fixes the pipe, and the crew removes water and dries the structure.
- Main valve closed
- Standing water kept away from outlets and appliances
- Photos before anything is moved
- Insurer called early
- Plumber for the pipe, restoration crew for the water
What about a vacant or closed-up house?
A vacant house is where freezing is hardest to catch, because no one is there to notice a leak. Water can run for days. Keeping the heat on is the simplest protection, and shutting off and draining the system is another, though it is a job for a plumber. Have someone check the house regularly through the winter.
Homes left empty over holidays are found with water running for days. In a twin or row, the leak may also reach a neighbor, who then finds a stain on their ceiling before the owner knows anything is wrong.
A plumber can shut off the water at the main, drain the system and, where appropriate, advise on protecting drains and traps. That is a different approach from leaving the heat on, and it suits houses that will be empty for a long time. Which approach fits depends on the house.
If you are responsible for a rental or an inherited property, check your insurance policy for vacancy conditions. Some policies limit coverage for homes left empty beyond a set period, and your agent can tell you what yours says.
Frequently asked questions
How can I tell if a pipe is frozen?
A faucet that runs slowly or not at all, frost on a visible pipe or a pipe that feels very cold are common signs. If the other taps work, the frozen pipe is likely on one branch. If no water comes from any tap, the problem may be at the main.
Is a dripping faucet worth it on a freezing night?
Some utilities suggest it for lines on exterior walls, because moving water is harder to freeze and a drip relieves pressure. It is a precaution and not a guarantee. Ask your plumber what makes sense for your house.
Is a pipe that froze always going to burst?
No. Many pipes freeze and thaw with no split. A pipe that is bulging, cracked or leaking after a thaw has failed. If you are unsure, close the main valve after the thaw and look for water.
Will my homeowners policy pay for a burst pipe?
Sudden and accidental damage such as a burst pipe is often covered, while long-term leaks usually are not, and vacancy conditions can matter. Coverage is settled between you and your insurer. Check the wording of your policy with your agent, and the crew can supply moisture readings and photos for a claim.
Who fixes a burst pipe, and who dries the house?
The pipe itself is a licensed plumber's repair. A restoration crew removes the water, opens wet walls and dries the structure. They are separate jobs and can be scheduled around each other.
What if the water is coming from the street?
A broken water main or street-side pipe is the water utility's responsibility. In Philadelphia that is the Philadelphia Water Department. A crew can help stop water inside the house, cover an opening and clean up afterward, but it does not repair the main.
Sources
- City of Philadelphia – How historic winter storms in 2026 affected Philadelphia's utilities
- City of Philadelphia – Residents urged to prepare for prolonged below-freezing temperatures
- National Weather Service Mount Holly – Philadelphia climate normals
This guide is general information for Montgomery County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.